Switch Regulating a Fluctuating Voltage Input

[brenesrob]

I would like to use a switch regulator in order to regulate a voltage supply that changes from 17.5V when running off a solar panel and 7.2V when running off a battery. Is it possible to do this? The problem is that the inductor value for these circuits only covers a small range of voltages. I have used switch regulators in the past but for a fixed input voltage value not one that fluctuates over such a high range.

The current being drawn by the load after the regulator is of 0.5A and I would like to keep the circuit as efficient as possible.

[digsys]

...  changes from 17.5V when running off a solar panel and 7.2V when running off a battery .... I have used switch regulators in the past but for a fixed input voltage value not one that fluctuates over such a high range.

7.2 > 17.5V is NOT a large range for MANY DC-DC converters at all. You didn't specify what OP voltage you need?
If it is 6.0V or less, then your project is a piece of cake.

[brenesrob]

Sorry I forgot to mention it. My output voltage is of 5V for a USB connection.

[Psi]

http://www.digikey.co.nz/product-detail/en/R-78E5.0-0.5/945-1648-5-ND/2834904

There's even a through hole module that has the typical voltage regulator pin-out
http://www.digikey.co.nz/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781

Both look to be around 90% efficient